• Progress in Superconductivity and Cryogenics
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• v.11 no.3
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• pp.55-59
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• 2009

In attempts to closely study the effect of high efficiency, friendly environment HTS(High Temperature Superconducting) cable and SFCL(Superconducting Fault Current Limiters) on power system, several projects were carried out around the world. Promising results have been achieved in terms of cable capacity and reliability. commercial HTS cable and SFCL, however, must not only be only be feasible, but meet practical requirements as well. To facilitate the transition of HTS cable technology from the Lab. to the Real Grid, a New project for applying 22.9kV HTS cables and SFCL to the commercial Power Grid supported by Government has just started in KEPCO. Target of this project is to operate two 22.9kV, 50MVA, 150MVA HTS cables and two 22.9kV 630A, 3000A SFCL in a KEPCO Grid in order to demonstrate its reliability and stable operation. This paper will present the technology for selecting appropriate site and its plan for installation & operating of 22.9kV HTS cables & SFCL in KEPCO Grid.

• Progress in Superconductivity and Cryogenics
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• v.12 no.1
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• pp.37-41
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• 2010

To limit fault current in a power system, superconducting fault current limiters (SFCLs) using high temperature superconducting (HTS) coils have been developed by many research groups so far. Non-inductive winding of HTS coils used for SFCLs can be classified into solenoid winding and pancake winding. Each of winding is expected to have different quench and recovery characteristics because the structure of solenoid winding differs from pancake winding's. Therefore it is important to the SFCLs application to investigate characteristics of each winding. In this paper, we deal with quench and recovery characteristics of four kinds of winding : solenoid winding, pancake winding without spacers, and with spacers of 2 and 4 mm thickness. In order to obtain quench and recovery parameters of coils, short circuit tests were performed in liquid nitrogen.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.21 no.4
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• pp.503-516
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• 2023

A transfer cask serves as the container for transporting and handling canisters loaded with spent nuclear fuels from light water reactors. This study focuses on a cylindrical transfer cask, standing at 5,300 mm with an external diameter of 2,170 mm, featuring impact limiters on the top and bottom sides. The base of the cask body has an openable/closable lid for loading canisters with storage modules. The transfer cask houses a canister containing spent nuclear fuels from lightweight reactors, serving as the confinement boundary while the cask itself lacks the confinement structure. The objective of this study was to conduct a structural analysis evaluation of the transfer cask, currently under development in Korea, ensuring its safety. This evaluation encompasses analyses of loads under normal, off-normal, and accident conditions, adhering to NUREG-2215. Structural integrity was assessed by comparing combined results for each load against stress limits. The results confirm that the transfer cask meets stress limits across normal, off-normal, and accident conditions, establishing its structural safety.

• Progress in Superconductivity and Cryogenics
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• v.19 no.4
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• pp.1-11
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• 2017

This article reviews the recent activities of field testing and application of superconducting fault current limiters (SFCL) based on high-temperature superconductors (HTS). The review particularly focuses on the trends in the field tests in terms of the technical aspects and commercial activities of the SFCLs. Stimulated by the discovery of HTS, numerous research and development activities have been conducted worldwide for SFCLs operating from distribution voltages to transmission voltages. Different types of SFCLs have been developed and field-tested. Consequently, more than 20 field tests and applications have been performed on real grids worldwide while supplying electric power to the customers. These field tests have not only provided the track records of the operation experiences including the problems and maintenance during operation, but also proved their current limiting capabilities against real faults, rendering this new technology highly viable. Through these activities, the following trends in the status of field testing and application are observed. Resistive-type SFCLs with HTS-coated conductors were dominantly used in the most recent field tests. This implies that the resistive type is technically more mature than the other types. Bus-bar coupling and transformer feeders were the major application locations. It is of importance that most of the field applications were conducted as R&D projects. A relevant change from the R&D stage to the application stage is shown as recently deployed SFCLs are expected to be under long-term operation and commercial service. Here, we review the installation of these SFCLs by substation. This review also discusses the recent activities for their commercial applications.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.3
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• pp.398-402
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• 2008

Recently, the development of superconducting fault current limiters (SFCLs) has been required as power demands increase in the power system. A distribution-level prototype resistive SFCL using coated conductor (CC) has been developed by Hyundai Heavy Industries Co., Ltd. and Yonsei University for the first time in the world. The ratings of the SFCL are 13.2kV/630A at normal operating condition. A novel non-inductive winding method is used in fabricating coils so there is almost zero impedance during normal operation. The distribution SFCL is cooled by sub-cooled liquid nitrogen $(LN_2)$ of 65K and 3 bar to enhance cryo-dielectric performance, critical current density, and thermal conductivity. In order to make reliable operation of an SFCL in real power systems, we monitored and controled its operation conditions by using supervisory control and data acquisition (SCADA) method. Thus, a monitoring system for the SFCL employing information technology (IT) is proposed and developed to be on the lookout for the operation conditions such as inside temperature, inside pressure, $LN_2$ level, voltage and current. Since operation temperature should be kept constant, bang-bang control for temperature feedback with a heater attached to the cold head of cryo-cooler is applied to the system. Short-circuit tests with prospective fault current of 10kA and AC dielectric withstand voltage tests up to 143kV for 1 minute were successfully performed at Korea Electrotechnology Research Institute. This paper deals with the development of a distribution level SFCL and its monitoring system for reliable operation.

• Progress in Superconductivity and Cryogenics
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• v.13 no.1
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• pp.41-45
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• 2011

Hybrid fault current limiters (FCL) have been researched at Yonsei University. The hybrid FCL has advantages such as having a rapid response to a sudden fault situation and a fast recovery time from a quench. It consists of an asymmetric HTS coil, a switching module, and a bypass reactor. The asymmetric HTS coil is wound with two different types of HTS wires in an opposite direction so that it has nearly zero inductance at the superconducting state. When the quench occurs at the fault state, a strong magnetic field is generated from the asymmetric coil because of different quench characteristics of two HTS wires, and then a repulsive force is induced in the switching module. The force opens the switch and the fault current is pushed into the bypass reactor. In this research, we analyzed the cause of the repulsive force and confirmed, experimentally and computationally, that the magnitude of a repulsive force is varied by changing the gap distance between the asymmetric coil and the switching module. By using the FEM simulation, we calculated the repulsive force with respect to the gap distance and verified that the effect of the gap distance. Then, short circuit test was carried out to confirm the correct operation of the fast switch.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.2
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• pp.10-16
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• 2003

The unsteady supersonic flow over tandem cavities has been analyzed by the integration of Navier-Stokes equations with the k-$\varepsilon$ turbulence model. The unsteady flow is characterized by the periodicity due to the mutual relation between the shear layer and the internal flow in cavities. The upwind TVD scheme based on the flux vector split with the van Leer limiters is used. The results show the principal frequency is very reasonable. The principal frequency of the rear cavity due to the front cavity has been analyzed by the combination of the several aspect ratios of cavities. In the case of the front cavity of low aspect ratio, the frequencies of tandem cavities are almost same, because two shear layers developed from each cavity are mixed and developed to one shear layer. However, in the case of the front cavity of high aspect ratio, the characteristis of frequency are very different, because the second shear layer is developed in the diffused first shear layer.

• Progress in Superconductivity
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• v.13 no.3
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• pp.189-194
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• 2012

Studies on the development of high voltage superconducting apparatuses, such as transmission superconducting fault current limiters (SFCLs) and superconducting cables, have been performed worldwide. In this paper, a study on the electrical insulation characteristics of electro negative gas according to various pressures and utilization factors was conducted as a part of developing a high voltage superconducting coil with a sub-cooled nitrogen cooling system. Some gases such as helium (He), nitrogen ($N_2$), and sulfur hexafluoride ($SF_6$) are considered for pressurizing the sub-cooled nitrogen cooling system of high voltage SFCLs and superconducting cables. $SF_6$ is used to pressurize and enhance the dielectric performance of a superconducting system of a sub-cooled nitrogen cooling system for superconducting cables being developed in the Republic of Korea. In this paper, dielectric experiments on AC voltage, as well as lightning impulse voltage of $SF_6$, are conducted according to various utilization factors by using several kinds of sphere-to-plane electrode systems. As results, it is known that the empirical formulae of $SF_6$, known as an electro negative gas, are derived according to various pressures and utilization factors. Also, the appropriate pressure condition for designing a high voltage superconducting coil is found from the viewpoint of dielectric performance.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.2
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• pp.277-281
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• 2007

We investigated fault current limitation characteristics of the resistive superconducting fault current limiter (SFCL) which consisted of a Bi-2212 bulk coil and a shunt coil. The Bi-2212 bulk coil and the shunt coil were connected in parallel. The Bi-2212 bulk coil was placed inside the shunt coil to induce field-assisted quench. The fault test was conducted at an input voltage of $200V_{rms}$ and fault current of $12kA_{rms}\;and\;25kA_{rms}$. The fault conditions were asymmetric and symmetric, and the fault period was 5 cycles. The test results show that the SFCL successfully limited the fault current of $12kA_{rms}\;and\;25kA_{rms}$ to below $5.5{\sim}6.9kA_{peak}\;within\;0.64{\sim}2.17$ msec after the fault occurred. Limitation was faster under symmetric fault test condition due to the larger change rate of current. We concluded that the speed of fault current limitation was determined by the speed of current rise rather than the amplitude of a short circuit current. These results show that the Bi-2212 bulk coil is suitable for distribution-class SFCLS.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1034-1035
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• 2015

Watertight 25.8 kV/600 A/12.5 kA fault current limiters (FCLs) have successfully installed in five areas (Incheon, Seoul, Gyeong-gi, Daejeon, Suwon) on KEPCO power distribution line for the purpose of commercial demonstrations. The fault current limiting operation of this FCL, which includes functions of sensing, commutation, and reduction of fault currents, is perfectly completed within 1 cycle immediately after fault occurs. The performance of FCL was verified by short circuit test, impedance test, insulation test, temperature-rise test, and control test, etc at PT&T in LS industrial systems, which is the official certification institute in Korea. In 2013, and also the FCL field test was performed in order to test the protection coordination between conventional relays and FCL, on the 1.5 kA and 5.0 kA faults, which were made by connecting the Artificial Fault Generator (AFG) to the distribution line in test grid at KEPCO Power Testing Center. The next step of this project is to check the FCL conditions caused by real external environment, and acquire the various data from five regions installed with FCL. In this paper, we intend to explain the FCL specifications and performance characteristics, and check the expected effect by application of FCL to power distribution line based on the power system analysis of an application site.